I am not good at making addons, however I have an idea if you havent addressed this yet.

Keep how the mushrooms are shown, as little yellow dots, however they are transparent, and where every bit of healing happens the dots become more solid in color. I have no idea how viable something like that could be made, however I just would like to make that suggestion.

The other idea that I had was, if the above idea didnt work just have them be different colors. Like a stoplight. When they are first laid down they are red, then at 50% yellow and at full green.

Again no idea how viable that is, but some sort of tracking for this would be greatly appreciated!!!